The nitrogen in the atmosphere of Saturn's moon Titan seems to have gotten its start as ammonia ice in the early solar system. The finding suggests that the essential building blocks of Titan formed under similar conditions as ancient comets in the Oort cloud, not in the warm disk that surrounded Saturn when the planet was young, researchers report June 20 in Astrophysical Journal Letters.

ESA’s Rosetta mission could confirm the results later this year when it studies comet 67P/Churyumov-Gerasimenko. The comet is from the Kuiper Belt and should have slightly different chemistry than anything originating in the Oort cloud.

The results also provide hints as to how Earth got its atmospheric nitrogen, the scientists say.